The hydrosilylation reaction between the organohydrogenpolysiloxane and an olefinically substituted polyoxyalkylene reactant is typically performed in a low molecular weight volatile hydrocarbon solvent such as benzene, toluene, xylene or isopropanol to promote the solubility of the reactants, to aid in handling the reactants or to moderate an exothermic reaction. Less typically, the hydrosilylation reaction may be conducted without a solvent such as disclosed in U.S. Pat. No. 3,980,688 or conducted in an oxygen containing solvent such as a higher molecular weight alcohol.
For example, U.S. Pat. Nos. 3,280,160 and 3,401,192 disclose the preparation of copolymers in n-butylether and in a 50/50 mixture of isopropyl alcohol/toluene, respectively. In U.S. Pat. No. 4,122,029 the use of isopropyl alcohol is disclosed and in U.S. Pat. No. 3,518,288 the patentee teaches the use of n-propanol/toluene as a suitable solvent for the preparation of siloxane-oxyalkylene copolymers. The particular solvents employed in U.S. Pat. No. 4,857,583 are saturated polyols containing two or more hydroxyl groups. U.S. Pat. No. 4,857,583 states that if one were to use copolymers containing monohydric higher alcohols in urethane foam applications, these alcohols will enter into the urethane reaction and act as reaction chain terminators in a detrimental fashion because they contain only one hydroxyl group.
The reaction may also take place in a monocarboxylate ester of an alkanediol solvent as disclosed in U.S. Pat. No. 4,153,293 to Hales, et al. These solvents are advantageous because monocarboxylate ester solvents do not need to be stripped and recovered from the product. In addition, the monocarboxylate ester solvents are not hygroscopic, and therefore the problems associated with water contamination are alleviated. Of the above mentioned solvents, isopropyl alcohol (IPA) and toluene are the most common solvents used.
Silicone polyethers containing polyether groups greater than 10-12 EO units tend to form a hazy 2nd phase layer upon standing. This is generally believed to be due to unreacted allyl polyether which is added in excess to the reaction to facilitate complete consumption of the silicone hydride. The excess polyether (of EO chain length greater than EO 10-12) has a freeze point near or below room temperature. Thus, the excess freezes and causes the 2nd phase to form. This is problematic in numerous product applications such as personal care, where the appearance of the material is an indication of its' purity, as well as in industrial applications such as polyurethane foam making. In the manufacture of polyurethane foams, a 2nd phase which can settle to the bottom of a drum or tank can cause nonuniform feeds of surfactant into the foam making process. This causes variation in the performance of the surfactant.
In contrast to the teachings of the prior art, the present invention utilizes a phenyl ether solvent. The present inventors have discovered that phenyl ether solvents not only act as a solvent during hydrosilylation but improve the clarity and reduce the freeze point of the surfactant without a sacrifice of other properties. The phenyl ether solvents also do not need to be stripped and recovered from the product, saving an entire process step over earlier methods. Furthermore, the phenyl ether solvents are not flammable. The phenyl ether solvent can also be added as a cold blend additive to a silicone polyether made in a solvent other than a phenyl ether.
It is therefore an object of the present invention to provide an improved process for the preparation of siloxane-oxyalkylene copolymers.
Another object of this invention is to provide a process for the preparation of siloxane-oxyalkylene copolymers.
It is a further object of this invention to provide a process for the preparation of siloxane-oxyalkylene copolymers which are useful in the formulation of urethane foams and which contain a phenyl ether solvent.
It is also an object of this invention to teach a process to reduce the haze in a surfactant.
These and other objects will readily become apparent to those skilled in the art in the light of the teachings contained herein.